Regent’s Canal, in which the dead body of an Italian carpenter named Sebastiano Magnanini was found bound to a shopping trolley two weeks ago, is by turns a beautiful and bleak throughway that runs half-hidden across north London. And the part that cuts through Islington is one of the most unpredictable of its rapidly changing sections.

A few hundred yards either side of the spot where Magnanini, a one-time art thief, was discovered, there are displays of urban decay and rejuvenation, a dumping ground of litter and bright new property developments. Not far off are pubs associated with the Adams family, the notorious north London crime organisation. And a short walk away is the Caledonian Road, a strip of ungentrified London that has more than its share of street crime, gangs and drugs.

But the place where Magnanini’s corpse was first seen by a passerby is a sublime section of old Islington, with charming narrowboats moored by a tree-lined stretch of the canal, below elegant streets of white-stuccoed townhouses. In other words, this is not where you would expect to encounter such a shocking scene.

It’s not unusual to find shopping trolleys that have been thrown into the canal, the flotsam of reckless or illicit misadventures, though usually they’re to be seen in the more neglected passages that are features of London’s post-industrial suburbs to the east and far west. And unfortunately it’s not unheard of to find bodies in there, too. The headless torso of the EastEnders actress Gemma McCluskie was discovered in the Hackney section of the canal in 2012. In 2014 the body of 14-year-old Alice Gross was found in the Brent river, effectively a tributary of the canal in north-west London. And earlier this year the body of Marta Ligman, a 23-year-old Polish woman, was found in a suitcase in the water at Maida Vale.

What does, however, seem to be unprecedented is a body and a shopping trolley stuck together. It’s as if unthinking hijinks and premeditated violence had been enjoined in the most disturbing fashion. None of the narrowboat residents milling about last week said that they had heard anything untoward during the time of Magnanini’s disappearance. He was last seen on Tuesday 22 September, and his was body was recovered two days later. “You just close your doors at night and put the music on,” said one resident. “You don’t hear what goes on outside.”

As he had no identification on him, the police released details of his distinctive tattoos, a carp on his torso, a lizard on his right shoulder, and smaller tattoos on his fingers. Last week the police confirmed that the dead man was Magnanini, an Italian national originally from Venice. The police announced that they were treating the death as suspicious, and a corpse bound to a shopping trolley in a canal is nothing if not suspicious. A murder investigation has been opened.

Because Magnanini was Italian and had a criminal past, there is inevitably speculation that organised crime was involved. And certainly something about the macabre nature of the death at least fits within a darkly theatrical tradition of mafia interventions, not least the murder of Roberto Calvi.

Just as Magnanini was found at the mouth of the canal’s Islington tunnel, so was Calvi, the Italian financier known as “God’s banker”, discovered hanging from below Blackfriars Bridge over the River Thames back in 1982. Initially the police thought the death was a suicide, but later realised that Calvi had been murdered in what was to became one of the most infamous unsolved crimes in modern British history.

Of course, aside from being Italian, Magnanini has little in common with Calvi, who was linked to the mafia, the Vatican and various other powerful forces within Italian society. By contrast Magnanini appears to have been a one-time petty criminal who briefly made a mark by stealing a notable artwork, Education of the Virgin, by Giovanni Battista Tiepolo, an 18th-century rococo artist. It was taken from the Santa Maria della Fava church in Venice in 1993. The painting was later found in a warehouse not far from Marco Polo airport outside Venice, and Magnanini was jailed for 18 months in the late 1990s. It was revealed last week that the case led to the arrest of members of Venice police’s flying squad, who were said to be working with the local mafia, the Mala del Brenta. Four police officers were sent to prison in 2004 on corruption charges, but by then Magnanini had left the country. He was thought to have moved to Plaistow in east London in 2003. And as far as anyone knows, that was the end of his career as an art thief. “He hasn’t been active since his initial foray into art theft,” said Art Recovery International’s Christopher Marinello, an expert in art crime.

Julian Radcliffe, of the Art Loss Register, an organisation that has liaised closely with European crime networks, said that he had no inside information on Magnanini. But he made the point that art criminals were not specialists, just generalists looking for the most profitable opportunity with the least risk. “I guess that the subject is drugs rather than fine art,” he added.

According to Magnanini’s younger brother, Matteo, Sebastiano worked as a freelance carpenter and had turned his back on crime and drugs. “He was a passionate guy, hardworking and creative. The man I knew certainly wasn’t a gangster. He did not seem the criminal type at all, just a genuinely good guy. I’m shocked.” The same descriptions were echoed by friends in Cambodia, where until recently he had been living. Luke MacKenzie, who befriended Magnanini in the far east, said that the Italian had been wrongly characterised in the press, and that he had put his criminal background long behind him.

“He didn’t talk about what happened in the past,” said MacKenzie. “He had told a few friends what he’d done, but just by knowing him you knew he was genuinely trying to turn over a new leaf. He was a new man and a wonderful human being who will be sorely missed.” He had apparently left Venice in 1999 and spent the last five years travelling around the world, teaching English in Colombia, Cambodia and Thailand.

He was listed on Facebook as living in Phnom Penh and on his page was a video of the 46-year-old playing guitar and singing outside a bar in Siem Reap in Cambodia. He’s with a few friends, the table is stacked with beers, and he looks like a man without a care in the world, enjoying life in the moment.

Sebastiano Magnanini in a video from his Facebook page. Photograph: Liam MacKenzie

It’s hard to credit the idea that someone as laidback and seemingly adrift from life in London, let alone Italy, could have been the subject of a longstanding feud or gangland score-settling. Scotland Yard detectives said last week that they did not believe that the death was linked to organised crime in Italy. But that inevitably raises the question of who was responsible, and what their motive was.

Magnanini was last seen around King’s Cross and the Caledonian Road at 7pm on 22 September. The area, just a couple of hundred yards from this newspaper’s office, has long been a meeting place for transient people, travellers, hustlers, and those on the margins of the law.

It’s the kind of area where people without very much hang out on street corners or in doorways looking to gain a little bit more. But a thousand meetings and transactions take place each day on these streets without anything major going wrong. Was Magnanini’s death to do with this rootless locality and one of those semi-innocent meetings? Or did he just have the misfortune to find himself in the wrong place at the wrong time with the wrong person or people?

On the canal path last week, next to where Magnanini was found, the dappled sunlight shone through the overhanging trees, people walked in shirtsleeves and the narrowboat residents went about their daily business. Life carried on and the canal was once again a pretty respite from the busy streets of London. The mystery of what took place in the last hours of the man from Venice’s life seemed to have retreated into the depths of the Islington tunnel. But given how active the area is, and how difficult it is to remain unseen, it’s unlikely that it will remain there.

This article was amended on 4 October 2015 because it referred to Christopher Marinello as “Christopher Marlowe”. This has been corrected.